Use of Pressure-Activated Sealant To Cure Leaks in Subsea Wells—A Case Study in Campos Basin

摘要

Offshore oil and gas production systems are complex systems comprised of wells, flow lines, a variety of subsea and dry subsystems, production platforms and export lines. Hydraulic systems are extensively used in offshore production systems, particularly for valves control and operation. Failures in hydraulics systems may cause loss of redundancy, loss of control and well shut-in with economic losses and risks to system integrity and environment. Leaks, mostly internal, represent one of the most common failures in the hydraulic systems. The conventional approach to repair these leaks makes use of rig and/or support vessels, being time and money consuming, not mentioning the risks imposed to the system under intervention. The difficulty, risks and costs increase with water depth. In the Campos Basin, offshore Brazil, with around 500 subsea wells, in water depths range from shallow to ultra deep, leaks in hydraulic systems have a significant impact on maintenance costs. Sensitive components are down- hole safety valves, wet christmas trees valves, annulus subsurface safety valves and subsea manifolds subsystems. These aspects made the search for reliable remote or light workover solutions an important issue. A promising solution was introduced in Campos Basin in the year 2000, which makes use of a pressure-activated sealant fluid. This paper presents a case study comprised of tens of pressure-activated sealant applications, both in fixed and floating systems, carried out in Campos Basin in the last four years. The paper summarizes the operational programs, the field reports, the post-job analyses and the results achieved. The study revealed that pressure-activated sealants are a safe and economic method to repair leaks in offshore hydraulic systems. As the number of offshore oil and gas production systems, mainly the floating ones, tends to increase considerably in the near future, the knowledge acquired in Campos Basin may be useful worldwide. The main differential of this paper is a thorough and critical review, from the operator point of view, of 71 applications from 01/21/2000 to 05/16/2005.